CO2 injection- levels wont rise

I just plumbed by CO2 back in and the indicator shows no change although its been running for 3 days and at a higher rate than Ive ever had it.
I've always had trouble with it though, seems I need alot of gas to get close.

Surface agitation is almost nill, just a slow swirl. No airstones.

I think this is a chemistry lesson to be learnt here. Somethings pinching it .
I have noticed a large amount of bubbles collecting in the gravel substrate but I'm unable to determine if this is chemical or the injection. I have an inline diffuser which is flat out and a few small bubbles are being exhausted into the tank. Some of these my be grouping in the gravel.

The reason I say a chemistry lesson, I've got a GH at 240ppm and KH at 210ppm. The way I understand it is KH acts as a buffer (mines large) by injecting CO2 I'm effectively attempting to lower the PH to which the KH is resisting? Currently my best measurement of PH is 7.5 (wide band kit )

Same problem here too. I'm using the pH controller reading to determine the CO2 level. My baseline pH is 7.0 but when adding CO2 I hit a stone wall when it reaches a pH of 6.0(30 ppm?). Last night I added a modified 24" salt water protein skimmer to act as a CO2 reactor and connected it to the output of the Sera CO2 Reactor 500 to see if that will help dissolve CO2 better. Last night I did see some pearling and also a few of those larger bubbles coming out of the sand(?) but the pH was still at 6.0.
I expect to see a difference when I go home from work today.

my reference water is from tank as per instructions. I have only just discovered this 4dkh business in the last hour, still reading.....

Either way theres no change in PH.

As you already have found out, using aquarium/tap water is not the correct method. Many drop checkers state to use aquarium/tap/RO/distilled etc water, but only when using a 4 dkH reference solution can you be sure of how much CO2 you are actually injecting.

Quote:

Originally Posted by CLAndrews

Same problem here too. I'm using the pH controller reading to determine the CO2 level. My baseline pH is 7.0 but when adding CO2 I hit a stone wall when it reaches a pH of 6.0(30 ppm?).

Similar to above, using a pH controller to measure pH as a determinant of how much CO2 is dissolved in the water column is misleading, as it will not give an accurate representation.

However, if you are reaching a full point drop in pH, then you are likely reaching close to 30 ppm.

KH does not make the water resist pH changes. All it does is raise the pH of the water - assuming there is some CO2 dissolved in the water, which there always is. So, even with 40 ppm of CO2 in the water your pH will still be relatively high. As Darkblade48 said, you need to use 4 dKH water, made from distilled water with nothing in it that affects the KH or pH other than carbonates or bicarbonates, in the drop checker (plus 2-3 drops of pH reagent). Then, when that water is green you have somewhere between 15 and 40 ppm of CO2 in the water.

I cant disagree with experience but im caught in the middle now. My test kit quotes "Carbonate hardness (KH) stabilizes water pH". Are they using it in the sense it resists Acidity. i.e buffer?
That to me suggest it prevents changes to pH

totallyconfused.com

Have ordered 4dkh reference solution from Egay. It helps if my measuring equipment is working correctly. The power of forums eh!

PH is merely a measure of the hydrogen ion concentration of a solution. It makes no measurment of calcium ions (GH) or carbonates (KH) whether they be calcium carbonate or sodium bicarbonate. This is why we have the term GH and KH. The chemical process of molecules exchanging hydrogen ions is known as the acid base balance system. It is based on Le Chatelier's principle. Which basically describes a state of chemical equilibrium. Those changes shift the PH up or down depending on the amounts of each chemical present.

GH is an abbreviation for general hardness. When we refer to water as being hard or soft, GH is the measurement that should be used. When a fish, plant or anything else is said to prefer hard or soft water, it is the GH measurment that is being referenced. GH is primarily a measurment of calcium ions (CA++).

KH is carbonate hardness. It does not refer to the actual PH of the water. To further confuse us it also is refered to as alakalinity which should not be confused with the term alkaline or base which is the opposite of acid. Carbonates ( that KH thing again) are used to "buffer" a solution. Imagine carbonates as a sponge. If we add an acid, the sponge will absorb it maintaining the PH at a constant level. When that sponge gets full the PH will begin to drop. So when our KH level is very low, any changes will result in a rapid and dramatic drop in PH.

CO2 can drive the system to the left by creating carbonic acid. This is why it is important to have your water in the drop checker at exactly 4KH. Otherwise the PH will not change at the expected rate (the water will not change color if the KH is too high and too fast if KH is to low).

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